Bilal, Essaid Chemical properties of helvite group minerals in different types of occurrences - Rotterdam A.A. Balkema 1991 - pp. 719-722 ilus. Subjects--Topical Terms: ASOCIACION MINERALGEOQUÍMICAHELVITAPARAGENESISPROPIEDADES QUIMICASSILICATOS Universal Decimal Class. No.: 553.21/.24/P16|4